City Research Online

Abstract

To investigate the progressive collapse resistance of steel frames with tree connections subjected to edge column failure along the major axis, ensuring the safety of structures under extreme conditions such as impact loads and fires, three full-scale beam-column substructures were designed and tested. The test variables included the presence of lateral restraints and temperature levels. Results indicate that edge column along the major axis failure transforms the substructure into an ultra-long cantilever beam, relying solely on flexural mechanisms for collapse resistance, unlike structures subjected to center column failure which benefit from catenary action. At room temperature, specimens without lateral restraints experienced overall instability, whereas lateral restraints shifted the failure mode to local buckling at the beam end, increasing bearing capacity by 13.1 %. Under high temperatures, laterally restrained substructures still exhibited overall instability due to material degradation. Finite element analysis further revealed that while vertical load magnitude minimally affects failure modes at high temperatures, fire resistance decreases with the vertical load increase on the failed column. When the beam end load increased from 18.68 kN to 32.69 kN, the critical temperature of the substructure decreased by 70℃. Finally, calculation methods for room temperature bearing capacity and load-dependent critical temperature are proposed. Validation against test and FEA results confirmed high accuracy.

Publication Type:	Article
Additional Information:	© 2026. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/
Publisher Keywords:	Steel frame, Edge column loss, Progressive collapse, Column tree connection, Fire resistance
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering
SWORD Depositor:	Symplectic Administrator

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